1. Field of the invention
This invention relates to a liquid crystal alignment film using a specific monomolecular film, a method of manufacturing the same, a liquid crystal display apparatus and a method of manufacturing the same.
More specifically, the invention concerns a liquid crystal alignment film used for plane liquid crystal display panels for displaying TV images and computer images, a method of manufacturing the same liquid crystal alignment film, a liquid crystal display apparatus using the same film and a method of manufacturing the same film.
2. Description of the Prior Art
With a liquid crystal display apparatus, it is necessary to provide an alignment film between the electrode surface and the liquid crystal composition in order to obtain normal operation with application of an electric field to the liquid crystal composition. The alignment film is necessary for conventional liquid crystal elements such as monochromatic and color liquid crystal elements.
A conventional color liquid crystal display panel will now be described.
The prior art color liquid crystal display panel has a structure, in which a liquid crystal is sealed between two substrates provided with opposed matrix array electrodes via liquid crystal alignment films formed by coating polyvinyl alcohol or polyimide with a spinner (i.e., by centrifugal spin coating).
FIG. 8 shows such a prior art color liquid crystal display panel. As shown, the apparatus has a first glass substrate 31 provided with a TFT (thin-film transistor) array 33 with pixel electrodes 32 and a second glass substrate 34 provided with pluralities of red, blue and green color filters 35, and transparent electrode 36. Liquid crystal alignment films 37 are then formed on top of the layers previously applied to glass substrate 31 and 34 by coating the substrates with polyvinyl alcohol or polyimide using a spinner and then polishing (or rubbing). These coated substrates are then assembled together by sealing them with adhesive 39 with a spacer 38 interposed between them. The sealed space is filled with twisted nematic (TN) liquid crystal 40 or the like, thus obtaining a panel structure. Polarizer 41 and 42 are disposed on the front and back sides of the panel, respectively. A color image is displayed on the apparatus in the direction of arrow A by operating TFT array 33 while illuminating the apparatus with backlight 43.
The alignment film is also necessary for other ferroelectric liquid crystals.
However, in the prior art the alignment film is produced by dissolving a resin such as polyvinyl alcohol or polyimide in an organic solvent, coating the solution by a rotational (or spin) coating method or the like and then polishing using a felt cloth or the like. Therefore, it is difficult to obtain uniform coating of an alignment film in the case of a large area panel (for instance a 14-inch display). In addition, with rotational coating the coating thickness is on the order of several microns. This results in great performance deterioration in the case of a display panel requiring an alignment film with a thickness of the order of 100 nm such as ferroelectric liquid crystals. For example, it is difficult to obtain a thin and uniformly thick coating of the resin component with conventional rotational coating techniques. In addition, it is difficult to carry out the polishing with a uniform pressure. Further, if the glass substrate has slight surface irregularities or if the resin component film has thickness irregularities, recessed portions fail to be polished.